1. Field of Invention
The invention relates generally to communication modules and in particular to a gasket for reducing the amount of electromagnetic interference (EMI) emitted from a module during operation.
2. Relevant Technology
Fiber optics are increasingly used for transmitting voice and data signals. While optical communications provide a number of advantages, the use of light as a transmission medium presents a number of implementation challenges. In particular, a number of protocols define the conversion of electrical signals to optical signals and transmission of those optical signals, including the ANSI Fibre Channel (FC) protocol. The FC protocol is typically implemented using a transceiver module at both ends of a fiber optic cable. Each transceiver module typically contains a laser transmitter circuit capable of converting electrical signals to optical signals, and an optical receiver capable of converting received optical signals back into electrical signals.
Typically, a transceiver module is electrically interfaced with a host device—such as a host computer, switching hub, network router, switch box, computer I/O and the like—via a compatible connection port. Moreover, in some applications it is desirable to miniaturize the physical size of the transceiver module to increase port density, and therefore accommodate a higher number of network connections within a given amount of physical space. In addition, in many applications, it is desirable for the module to be hot-pluggable, which permits the module to be inserted and removed from the host system without removing electrical power. For example, the Small Form-factor Pluggable (“SFP”) Transceiver MultiSource Agreement (“MSA”) was implemented to standardize the physical size and shape of optical transceiver modules to insure compatibility between different manufacturers. In SFP modules, usually a transceiver module is selectively removable from a port which is fixedly attached to the chassis or housing of the host device.
Another design consideration is the amount of electromagnetic interference (EMI) that is radiated by a certain component, module, or system. Equipment such as high speed data systems generate and transmit many signals in the radio frequency portion of the electromagnetic spectrum. EMI radiation is of concern because interference to other components or equipment may result if sufficient power from these signals escapes the equipment enclosures. Such interference may result in malfunctioning of some or all of the electronic system. EMI radiation may also limit the density of components in the system. Various national and international regulatory agencies (e.g., FCC, CISPR, etc.) have set limits for EMI emissions.
Nevertheless, many conventional transceiver configurations lack the ability to adequately reduce EMI emissions. Furthermore, as data rate gets higher and EMI emissions increase in frequency, conventional EMI shielding mechanisms that worked for lower-frequency emissions sufficiently well are becoming inadequate. Therefore, there is a need for a method and mechanism for providing adequate EMI shielding when even a high-data rate optical transceiver module is disposed in the host port. This method and/or mechanism also has to comply with existing standards. Such a module having adequate EMI shielding would allow a host system to provide a higher packing density, and yet allow the use of a small form factor transceiver module that complies with existing sizing standards.